6,1,8
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To be a 3 digit palindromic number, it must be of the form aba.I assume that a 3 digit number must be at least 100 (so that 020 for example does not count as a 3 digit number):a can be any of the nine digits 1-9;for each of these b can be any of the ten digits 0-9Thus there are 9 x 10 = 90 three digit palindromic numbers.
Squares of primes.
All numbers that are the square of primes have exactly 3 factors.
The squares of all prime numbers above 2 have exactly 3 factors.
Numbers with exactly three factors are squares of prime numbers.